Medical devices such as implantable medical devices (IMDs) include a variety of devices that deliver therapy (such as electrical simulation or drug delivery) to a patient, monitor a physiological parameter of a patient, or both. IMDs typically include a number of functional components encased in a housing. The housing is implanted in a body of the patient. For example, the housing may be implanted in a pocket created in a torso of a patient. The housing may include various internal components such as batteries and capacitors to deliver energy for therapy delivered to a patient and/or monitoring a physiological parameter of a patient.